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How does infectious arthritis develop after bacteria enter a joint?

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Once bacteria infiltrate the joint space, they trigger an acute inflammatory response characterized by the formation of pus. This pus, which develops in response to pathogens such as Staphylococcus, Streptococcus, or Pneumococcus, is highly destructive to the joint environment.123

Specifically, the accumulation of pus erodes the articular cartilages. Because these cartilages possess almost no capacity for regeneration, this erosion can lead to permanent joint damage if the infection is not treated promptly with antimicrobial therapy and drainage.3

In addition to direct bacterial infiltration, infection can reach the joint through three primary routes:
* The circulatory system: Bacteria travel via the bloodstream and enter through synovial blood vessels.12
* Direct contamination: Microorganisms are introduced through penetrating trauma or surgical procedures.12
* Extension: The infection spreads from adjacent bony infections, such as osteomyelitis, into the joint through natural or pathological openings in the bone cortex.2

Regardless of the entry method, the resulting septic arthritis typically causes systemic symptoms like fever alongside localized swelling, heat, and pain.23